Load Balancing and NAT on Cisco 1721

[prouteus]

Need some assistance on this. I've searched on the forums for questions regarding load balancing and NAT, but nothing really stands out as an answer.

Here's the problem:

We have a Cisco 1721 router with two WAN interfaces (1 Serial, and the other Ethernet). These two interfaces are going to seperate ISP's -- Frame on the Serial interface, and cable modem on the Ethernet interface. We want to provide load balancing and fail-over on both the WAN interfaces, and I understand that we can simply add two default routes of the same metric, which should do the trick. Although, when we do this, the router does not route at all! We have to remove one of the default routes in order to get traffic flowing again. I believe our problem may be related to NAT, which is required on both of the WAN interfaces. We are using a full private Class A in our network (10.0.0.0/8).

Here is the config we're trying to use. Does anyone see anything wrong with this, and why it might not work? I also noticed that the ISP (who originally configured the router) added the "IP CEF" command -- which I believe can do "per-destination" load-balancing on it's own, but I haven't had any luck getting it to work.

Config:

version 12.3
service timestamps debug datetime msec
service timestamps log datetime msec
service password-encryption
!
hostname visclksft
!
boot-start-marker
boot-end-marker
!
enable password 7 XXXX
!
clock timezone cst -6
clock summer-time cdt recurring
no aaa new-model
ip subnet-zero
!
!
ip name-server 151.164.20.201
ip name-server 151.164.17.201
ip name-server 24.93.40.62
ip name-server 24.93.40.63
!
ip cef
!
!
!
!
interface Ethernet0
description TMC RR (Tech Support: 512-531-2321)
ip address 24.242.X.X 255.255.255.252
ip nat outside
full-duplex
!
interface FastEthernet0
description TO LOCAL LAN
ip address 10.1.1.254 255.0.0.0
ip nat inside
speed 100
full-duplex
!
interface Serial0
description SBIS CKT 45.HCGM.009184/SBCIS Tech Support:866-937-3664
no ip address
encapsulation frame-relay IETF
no fair-queue
service-module t1 timeslots 1-24
frame-relay lmi-type ansi
!
interface Serial0.1 point-to-point
ip address 69.150.X.X 255.255.255.252
ip nat outside
frame-relay interface-dlci 16
!
ip nat inside source list 1 interface Serial0.1 overload
ip nat inside source list 2 interface Ethernet0 overload
ip classless
ip route 0.0.0.0 0.0.0.0 24.242.X.X
ip route 0.0.0.0 0.0.0.0 69.150.X.X
no ip http server
!
access-list 1 permit 10.0.0.0 0.255.255.255
access-list 2 permit 10.0.0.0 0.255.255.255
access-list 12 permit 10.0.0.0 0.255.255.255
!
line con 0
password 7 XXXX
login
line aux 0
transport input all
flowcontrol hardware
line vty 0 4
access-class 12 in
password 7 XXXX
login
!
sntp server 151.164.243.13
end

Any suggestions would be greatly appreciated. We're in a hurry to get this going for the higher-ups!

Thanks!

 

[webnetwiz]

You're trying to load balance the connections for traffic destined to the internet? You may want to try the backup command, with the load option, and set the load option to low so that even with low load, the second interface would come up to send traffic.